As a circuit system that generates a PWM signal used in a three-level power conversion device, a control circuit for a power conversion device that specializes in the three-level power conversion device and that realizes a PWM control system is known, for example, as described in the patent documents described below.
Japanese Laid-Open Patent Publication No. 2006-109541 discloses a control circuit for a power converter that realizes a PWM control system in which a high-speed current control response can be made, and in which harmonics can be suppressed and a switching frequency does not change significantly, in a three-level converter.
Japanese Laid-Open Patent Publication No. 2013-158093 discloses a three-level inverter in which control means for controlling each of three phases, U, V, and W, performs PWM processing by using a modulation signal λ from modulation signal generation means and a carrier signal from carrier signal generation means so as to generate a control signal that controls switching elements T1 to T4 of a switching leg of each of the phases.
Japanese Laid-Open Patent Publication No. 2014-103748 (see, for example, paragraph 0029 and FIG. 1 therein) discloses a control circuit of a power conversion device that specializes in a multilevel inverter of three or more levels, and that realizes a PWM control system, and further discloses that a control unit for power conversion is configured by an application specific integrated circuit (ASIC) or the like.
The patent documents above disclose a PWM control device that principally specializes in a three-level power conversion device. However, a PWM control device for a two-level power conversion device and a PWM control device for a three-level power conversion device are not compatible with each other, and therefore a PWM control device (a PWM signal generation device) may be individually prepared for each of the PWM control devices.